Today, I became an official "old timer" and eligible for Medicare.
I ride 25+ miles three or four times a week and try to get in at least one additional 50+ mile ride a week. I have no "recovery time" between rides.
My understanding of recovery time, based only on my 40+ years of serious running and riding, is that I need to rest a day or two only after near max efforts that extend over many hours. For example - a mountain bike ride that climbs 3000' in a couple hours in 85 degree heat.
Wednesday I rode 53 miles at a 15.1 mph pace, including over 2,000' of climbing - that seemed to be a medium effort ride for me so Thursday I rode 15 miles around town at a nice sightseeing pace. I guess you would say Thursday was a recovery day but it did include some exercise to stretch and loosen all my muscles.
Benefits of longer rides:
1) I can drink more beer after the ride without gaining weight
2) I get to see a lot more interesting scenery
3) I get to visit places I wouldn't normally visit
4) I feel like I have accomplished something even more worthwhile
5) I feel like I have time to stop and take some pictures
6) I don't feel like I have to do "intervals" that stress my cardio-vascular systems
7) I feel like I can just ride for the fun of it
As you suspect - bike fit, cadence and speed (level of effort) are important for doing an age over-60 longer distance ride.
I have spent years getting my Specialized Roubaix Triple setup to be comfortable - I can ride two hours non-stop in relative comfort. My saddle is seven years old and fits me perfectly. I make very small saddle height adjustments depending on how my old stiff knees ( 7 surgeries) feel on any given day. I rotate my handlebars very small amounts to accommodate my old gimpy shoulders, elbows, and wrists (three dislocated shoulders, two broken collar bones, dislocated elbow, and two broken wrists) as they demand each day.
When riding long distances I try to spin at 85 - 95 rpm most of the time. But once every 15 or 20 minutes I go to a MUCH higher gear, standup and really hammer for a couple minutes - that gets my heart pumping and stretches my legs nicely.
The big difference for me when riding longer distances (more than 40 miles) and shorter rides is that I pay attention to my short ride average speed and try to keep it at whatever target I set. When riding more than 40 miles I just ride whatever pace feels comfortable and don't pay much attention to my average. The key is COMFORT - my long rides are for enjoyment and comfort.
When riding more than 50 miles - I stop every 45 - 75 minutes to eat a little, take a picture or two, and stretch my back. But - I never stop for more than 5 minutes so that my legs and back don't have a chance to tighten up.
The biggest problem I see with consistently riding long distances is that those rides are addictive - the more I do long rides - the longer the rides get!